A strain gauge is a well known device that can be used to measure the strain being exerted on an object. In particular, for example, a strain gauge may be attached to a stressed section of a scale platform to determine the amount of force or strain exerted on the corresponding section. The amount of force or strain measured can then be used to determine the weight of the load on the scale platform.
An electronic transducer, also known as a load cell, operates utilizing four or more strain gauges wired together to establish a Wheatstone bridge electrical circuit. The load cell has become a relatively popular method of accomplishing commercial weighing. The load cell converts a mechanical movement associated with an applied force into an electrical signal. Thus, load cells can be particularly susceptible to environmental conditions which may impact the accuracy of the load cells. Outdoor environments or other environments in which shock and/or vibration may be encountered can present challenging environments for load cells relative to providing accurate results. Accordingly, continual and often costly maintenance programs and/or the use of additional components had been required to try to ensure continued accuracy of the scales that employed these load cells.
The Weigh-Bar® was developed to overcome some of the sensitivities of the traditional load cell, including side loads, end loads, torsion loads shock loads and vibration loads. This is accomplished via a combination of a large cantilever loading element and arranging the strain gages in a differential pattern within the Wheatstone bridge, as opposed to the maximum signal pattern used with traditional load cells. Other than the load cell body size, orientation and Wheatsone bridge arrangement, the Weigh-Bar® and load cell are very similar from a manufacturing standpoint.
Generally speaking, the strain gauges (or electronic sensors) of the load cell are positioned on outside surfaces of the load cell body. A simple potted seal may be employed along with the relatively rugged design of the load cell to avoid the use of a complex vacuum-type hermetic seal that would typically be used with a load cell. The load cell itself (e.g., when configured as a Weigh-Bar®) may be provided as a steel structure with two pairs of electronic sensors (e.g., a top pair and a bottom pair) disposed along an external surface of the load cell. The load cell may be positioned in a cantilevered arrangement, fixed at one end and unsupported at the other. When a force is applied to the unsupported end, a strain is generated along the length of the load cell. The top pair and bottom pair of electronic sensors (or strain gauges) each measure the strain at their respective locations along the load cell. Each respective location of the sensor pairs represents a separate corresponding bending moment. By comparing the respective strain measurements, the weight of the load on the load cell can be accurately determined while undesirable effects related to end loading, side loading and torsion effect can be minimized or eliminated.
Although the use of Weigh Bars® and load cells employing strain gauges in the manner described above is common, improvements in the design and performance of such Weigh Bars® and load cells may still be desirable.